Mjollnir played a crucial role at Creature Labs, as Sparky later explained in the forums:
"Mjollnir was a special case. It all stemmed from the time when CL was starting to run short of cash and we needed to make economies. One of these was to move the DS servers out of the co-location facility (deep in a concrete bunker) and back to Cambridge.
The trouble was to do so would have meant potentially days of downtime as this would have meant address changes. We didn't want that.
What we needed was a hammer to crack a nut, so we used Thors hammer ;-) All this machine had to do was to pretend it was the machines in co-lo and pass on traffic to and from these machines. So after a little head scratching we set it up, tested it and then switched the IP addresses over at the name servers.
We then waited, DNS changes can take a while, for activity to start...
After about four days we then made a trip to the co-lo and brought out half of the servers (they were all paired up for redundancy) and reinstalled them in Cambridge. We let these settle down for a day or two and then went to get the rest.
If I remember rightly, the only downtime we had was when we moved Ronnie (the Mall server, named after one of the Kray twins) as we didn't have a pair for that machine (which would, if we'd had one, been called Reggie). Even then, Mjollnir stepped in and put up a nice message saying something, so whilst the Mall wasn't running it still appeared to be there.
With the move complete, Mjollnir stayed on and continued to operate in a new role as a web-accelerator, kind of a proxy in reverse. This meant that the web-servers didn't have to serve static content and could hence concentrate on dynamic content.
And then everything went horribly wrong ;-)
When we put together the temporary (and still running, hmmm) system, I decided to once more use Mjollnir as that already had everything in place that we needed to handle the various problems that would come up with most of the system missing."